Higher animals including man each carry approximately 100,000 genes, but only about 15% thereof is expressed, and characteristics of individual's biological processes, e.g., genesis, differentiation, homeostasis, responses to stimuli, control of cell division cycle, aging and apoptosis (programmed cell death), are determined depending on which genes are expressed (Liang, P. and A. B. Pardee, Science 257: 967–971, 1992).
Pathogenic phenomena such as tumorigenesis are caused by gene mutation which brings about changes in the mode of gene expression. Therefore, comparative studies of gene expressions in various cells have been conducted to provide bases for establishing viable approaches to the understanding of diverse biological phenomena.
It has been reported that tumorigenesis is caused by various genetic changes such as the loss of chromosomal heterozygosity, activation of oncogenes and inactivation of tumor suppressor genes, e.g., p53 gene (Bishop, J. M., Cell 64: 235–248, 1991; and Hunter, T., Cell 64: 249–270, 1991). Further, it has been reported that 10 to 30% of human cancer arises from the activation of oncogene through amplification of protooncogenes.
Therefore, the activation of protooncogenes plays an important role in the etiology of many tumors and there has existed a need to identify protooncogenes.
The present inventors have endeavored to unravel the mechanism involved in the tumorigenesis of cervical cancer; and, have unexpectedly found that novel protooncogenes, human cervical cancer proto-oncogene 1 (HCCR-1) (Korea Patent Application No. 2000-16757 (Mar. 31, 2000)) and HCCR-2 (Korea Patent Application No. 2000-71202 (Nov. 28, 2000)), are specifically overexpressed in cancer cells. Protooncogene causes quantitative and qualitative changes of the corresponding protein product expression via a conformational change (Weinberg, R. A., Cancer Research 49:3713–3721, 1989). The conformationally changed-cancer protein destroys signal transduction pathways in the cell surface, cytoplasm or nucleus; while in the absence of tumor suppressor gene product, it stimulates cell proliferation together with other cancer proteins, disturbs cell cycle, and destroys cell death (apoptosis) mechanism (Todd, R., Anticancer Research 19:4729–4746, 2000).
The yeast two-hybrid method, developed in 1989 by Fields et al. (Fields, S. and Song, O., Nature 340:245–246, 1989) for examining such protein-protein interactions, has been widely applied to elucidate the cell death mechanism (Wallach, D. et al., Curr. Opin. Immunol. 10:131–136, 1989) as well as other biological processes using various genetic tools (Pandey, A. and Mann, M., Nature 405:837–846, 2000).
In the course of screening for a novel binding protein to protooncogene KG-19 using the yeast two-hybrid method, the present inventors have discovered a novel human protooncogene, KG-20 which expresses a protein that specifically binds to protooncogene KG-19. Protooncogene KG-20 can be advantageously used in diagnosis, prevention and treatment of various cancers, e.g., leukemia, lymphoma, colon, breast, kidney, stomach, lung, ovary and uterine cancers.